ScienceShot: Gold Mining and the Damage Wrought

There’s a gold rush going on in the Peruvian state of Madre de Dios, resulting in deforestation, runoff, and, as Science reported last month, mercury pollution. But because most of this mining is small-scale, clandestine, and illegal, researchers have had a hard time calculating its true extent. Now, a team of scientists has collaborated to accurately map Madre de Dios’s gold mines in space and time. The image above, created with new high-resolution satellite mapping techniques, shows the spread of gold mining along the Madre de Dios River between 1999 and 2012. Pink represents mines present before 1999; blue and green illustrate the spread during the middle of the 2000s; and yellow, orange, and red capture the mining that has sprung up since 2008. In 13 years, small-scale mining operations increased by 600% and the amount of land in the state affected by gold mining quadrupled, the researchers report online today in the Proceedings of the National Academy of Sciences (PNAS). Today, gold mining gobbles up an average of 6145 hectares of rainforest per year in Madre de Dios—more than three times the rate before the 2008 financial crisis drove up the demand for gold. And as another paper in PNAS this week shows, it’s nearly impossible to clean up after gold mining: Mercury pollution from the 19th century California gold rush will likely persist in the environment for more than 10,000 years.